Process for preparing radiation sensitive materials

ABSTRACT

A DISPERSION OF A RADIATION SENSITIVE SILVER HALIDE WITH A HEAVY METAL SALT OF A FATTY ACID IN A LIQUID MEDIUM IS PREPARED BY (A) PROVIDING AN OLEOPHILIC PRECIPITATE CONTAINING A RADIATION SENSITIVE SILVER HALIDE AND A SURFACTANT WHICH HAS THE PROPERTY OF MAKING THE SILVER HALIDE OLEOPHILIC, (B) DISPERSING THE OLEOPHILIC PRECIPITATE IN A SOLUTION OF AN ALKALI METAL OR AMMONIUM SALT OF A FATTY ACID AT LEAST AT A TEMPERATURE AT WHICH THE FATTY ACID SALT IS MAINTAINED IN SOLUTION, THEN (C) LOWERING THE TEMPERATURE AND PH OF THE PRODUCT OF (B) UNTIL SUBSTANTIALLY ALL OF THE FATTY ACID COMPOUND IS PRESENT IN THE SOLUTION AS A SOLID PHASE, AND THEN (D) CONVERTING AT LEAST PART OF THE FATTY ACID COMPOUND TO A HEAVY METAL SALT BY ADMIXING A SOURCE OF HEAVY METAL IONS WITH THE PRODUCT OF (C). THIS METHOD IS CONVENIENTLY CARRIED OUT BY MIXING A RADIATION SENSITIVE SILVER HALIDE GELATINO EMULSION WITH THE SURFACTANT IN (A). (A) AND (B) CAN BE CARRIED OUT BY PRECIPITATING THE RADIATION SENSITIVE SILVER HALIDE IN A SOLUTION OF THE ALKALI METAL OR AMMONIUM SALT OF THE FATTY ACID. THIS PROCESS ELIMINATES THE NEED FOR BALL MILLING AND PERMITS PREPARATION OF A PARTICULATE SOLID SUITABLE FOR MIXING THE COMPONENTS OF PHOTOSENSITIVE MATERIALS FOR PROCESSING WITH HEAT.

United States Patent 3,761,273 PROCESS FOR PREPARING RADIATION SENSITIVE MATERIALS Warren J. Miller, Rochester, and Ralph W. Baxendale,

Williamson, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y. No Drawing. Filed Oct. 1, 1971, Ser. No. 185,826 Int. Cl. G03c 1/06, 1/38 U.S. Cl. 96-94 27 Claims ABSTRACT OF THE DISCLOSURE A dispersion of a radiation sensitive silver halide with a heavy metal salt of a fatty acid in a liquid medium is prepared by (A) providing an oleophilic precipitate containing a radiation sensitive silver halide and a surfactant which has the property of making the silver halide oleophilic, (B) dispersing the oleophilic precipitate in a solution of an alkali metal or ammonium salt of a fatty acid at least at a temperature at which the fatty acid salt is maintained in solution, then (C) lowering the temperature and pH of the product of (B) until substantially all of the fatty acid compound is present in the solution as a solid phase, and then (D) converting at least part of the fatty acid compound to a heavy metal salt by admixing a source of heavy metal ions with the product of (C). This method is conveniently carried out by mixing a radiation sensitive silver halide gelatino emulsion with the surfactant in (A). (A) and (B) can be carried out by precipitating the radiation sensitive silver halide in a solution of the alkali metal or ammonium salt of the fatty acid. This process eliminates the need for ball milling and permits preparation of a particulate solid suitable for mixing the components of photosensitive materials for processing with heat.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a method of preparing a dispersion of radiation sensitive silver halide and a heavy metal salt of a fatty acid suitable for photosensitive and thermosensitive compositions, such as photothermographic materials. In one of its aspects it relates to a method of preparing such a dispersion employing a temperature and pH range which provides desired reaction conditions. In another aspect of the invention the method relates to preparation of photosensitive and thermosensitive compositions and elements containing the described dispersion.

DESCRIPTION OF THE STATE OF THE ART It is known that a mixture of silver behenate and behenic acid suitable for use in photosensitive and thermosensitive compositions and elements can be prepared by reacting an aqueous solution of silver nitrate with an aqueous solution of sodium behenate. Methods of preparing silver behenate are set out, for example, in U.S. Pat. 2,910,377 of Owen, issued Oct. 25, 1969; U.S. 3,152,904 of Sorensen and Shepard, issued Oct. 13, 1964; U.S. 3,457,075 of Morgan and Shely, issued July 22, 1969; U.S. 3,458,544 of Bryan, issued July 29, 1969; US 3,074,809 of Owen, issued Jan. 22, 1963; U.S. 3,107,174 of Wartman, issued Oct. 15, 1963; U.S. 3,218,166 of Reitter, issued Nov. 16, 1965; and U.S. 3,094,619 of Grant, issued June 18, 1963.

It is also known that photosensitive silver halide can be prepared in situ in the photosensitive and thermosensitive coatings of an element for processing with heat. Such a method is described in U.S. Pat. 3,457,075 of Morgan et al., issued July 22, 1969. For example, a

dilute solution of a halogen acid such as hydrochloric ice acid can be applied to the surface of the thin coating containing an organic silver salt, such as silver behenate, on a suitable support followed by removal of the solvent. This reference also indicates that the photosensitive silver halide can be prepared on silver behenate prior to application of the photosensitive silver halide on the support. For example, a halogen acid such as hydrochloric acid or hydrobromic acid can be mixed with an organic silver salt in a suitable reaction medium. A halide salt more soluble than the organic silver salt can be added to a suspension of the organic silver salt to form the silver halide. A suitable reaction medium includes Water which does not interfere with the reaction.

There has been a need to provide a process for preparing a dispersion of radiation sensitive silver halide and a heavy metal salt of a fatty acid for photosensitive and thermosensitive materials for processing with heat, e.g., photothermographic materials. The described processes, up to this time, have encountered one or more of the following problems: (a) the process involves use of an organic solvent which provides diflicult coating procedures and evaporation problems, (b) the process involves extensive ball milling or other undesired mixing procedures, (0) the process does not enable the use of conventional silver halide emulsion technology for preparation of a photosensitive and thermosensitive material, (d) the process does not enable the preparation of a particulate solid which can be stored as a dry powder, and/or (e) the dispersion does not provide radiation sensitive silver halide and, for example, silver behenate, which provides desired properties when mixed with other components of a photosensitive and thermosensitive composition for processing with heat. There has been accordingly a need to provide a process of preparing a dispersion which overcomes these problems.

There has also been a need to provide photosensitive and thermosensitive materials and elements for processing with heat which can employ a dispersion, as described, and which can be prepared employing simplified procedures.

SUMMARY OF THE INVENTION According to the invention, the described problems are overcome by preparation of a dispersion of a radiation sensitive silver halide with a heavy metal salt, especially a silver salt, of a fatty acid in a liquid medium by (A) providing an oleophilic precipitate containing a radiation sensitive silver halide and a surfactant which has the property of making the silver halide oleophilic, (B) dispersing the oleophilic precipitate in a solution of an alkali metal or ammonium salt of a fatty acid at least at a temperature at which the fatty acid salt is maintained in solution, then (C) lowering the temperature and pH of the product of (B) until substantially all of the fatty acid compound is present in the solution as a solid phase, and then (D) converting at least part of the fatty acid compound to a heavy metal salt, especially a silver salt, by admixing a source of heavy metal ions with the product of (C). This method is conveniently carried out by mixing a radiation sensitive silver halide gelatino emulsion with the surfactant in (A), (A) and (B) can be carried out by precipitating the radiation sensitive silver halide in a solution of the alkali metal or ammonium salt of the fatty acid. A dispersion of radiation sensitive silver halide and a heavy metal salt of a fatty acid in a liquid medium can be prepared, for example, by (A) admixing, in an aqueous medium, (i) a Water soluble alkali salt of a fatty acid and/or other suitable surfactant with (ii) a source of halide ions, at a temperature from at least a melting point of the fatty acid to about C., and then (B) admixing a source of silver ions in an aqueous medium, with the admixture from (A) at the described temperature; (C)

maintaining the temperature and pH of the reactant mixture at which the salt of the fatty acid is maintained in solution; then, after reaction completion; (D) lowering the temperature and pH until the desired dispersion is formed. This enables preparation of a particulate solid which is suitable for mixing with other components to provide a photosensitive and thermosensitive material for processing with heat.

DETAILED DESCRIPTION OF THE INVENTION A useful embodiment of the invention is a method of preparing a dispersion of radiation sensitive silver halide and a heavy metal salt of a fatty acid in a liquid medium comprising (A) admixing, in an aqueous medium, (i) a water soluble, alkali salt of a fatty acid with (ii) a source of halide ions, such as an aqueous solution of potassium bromide, at a temperature of from the melting point of the fatty acid to about 95 C., (B) admixing a source of silver ions, in an aqueous medium, with the mixture from (A) to provide a reactant mixture at the described temperature; (C) providing and maintaining the described temperature and the pH of the reactant mixture at levels at which the alkali salt of the fatty acid is maintained in solution; and mixing the reactant mixture until reaction completion; then (D) lowering the temperature and the pH of the reaction mixture until the desired dispersion is formed.

While the mechanisms of reaction and rates of reaction are not completely understood, it is believed that due to differences in, for example, solubility properties and reaction rates the radiation sensitive silver halide forms before the heavy metal salt of the fatty acid and that apparently the heavy metal salt of the fatty acid surrounds, at least partially, the radiation sensitive silver halide. The temperature of the reaction is chosen to provide a desired solubility of the fatty acid employed. The exact state of the various reactants at the temperature of the process is not completely understood. It appears that the fatty acid at the temperature employed is either in a molten state or is soluble in the combination of reactants employed.

A heavy metal salt of a fatty acid as employed herein, includes a range of heavy metal salts and a range of fatty acids. An especially useful class of heavy metal salt of fatty acids is represented by the water insoluble silver salts of long-chain fatty acids which are resistant to darkening under illumination. Compounds which are suitable silver salts include silver behenate, silver stearate, silver olcate, silver laurate, silver hydroxystearate, silver caprate, silver myristate and silver palmitate.

The reaction is carried out in an aqueous medium which includes water and water containing proportions of other components which do not adversely affect the desired reaction and dispersion of the radiation sensitive silver halide and heavy metal salt of the fatty acid.

A range of water soluble alkali salts of fatty acids can be employed in the described process. These include, for example, the water soluble alkali salts of behenic acid, stearic acid, oleic acid, lauric, acid, hydroxystearic acid, capric acid, myristic acid, and palmitic acid. Various alkali salts of these acids can be employed, but sodium and potassium salts are especially useful.

The described Water soluble alkali salts of fatty acids can be prepared employing conventional methods of preparation such as mixing a fatty acid as described with a suitable source of alkali, such as sodium hydroxide or potassium hydroxide.

The water soluble alkali salt of the fatty acid is believed to serve at least two functions in the process. It is believed to react with the source of silver ions and it is also believed to act as a surfactant. In the latter function, other suitable so-called surfactant compounds can be employed in the described process. Such other so-called surfactants which are suitable in the process include certain dyes, such as those containing a long-chain alkyl group,

e.g., 3' dioctadecyl thiocarbocyanine p-toluene sulfonate.

A suitable concentration of water soluble alkali salt of fatty acid will vary depending upon the particular reactant, reaction temperature, pH and the like. However, a suitable concentration is usually between about 0.005 mole per liter to about 0.5 mole per liter of water soluble alkali solvent fatty acid per .005 mole per liter of source of halide ions employed. For instance, when sodium behenate is employed with a source of bromide ions, the ratio concentration of sodium behenate to source of bromide ions is usually 1:1 to 100:1.

The mixture of the described water soluble alkali salt of fatty acid with the source of halide ion is carried out at a temperature of from at least the melting point of the fatty acid to about C. Below this temperature the reactants appear to form an undesired gel rather than a solution. The described elevated temperature is employed to provide the desired reactant solution or melt. A temperature should be avoided, however, which causes fogging of the silver halide produced.

Any source of silver ions can be provided in the process which provides the desired reaction with the water soluble alkali salt of the fatty acid. The source of silver ions is typically a water soluble silver salt, such as silver nitrate.

The mixing of the source of silver ions with the source of halide ions at the described temperature can be carried out with various mixing means and procedures commonly empoyed in the preparation of chemical and photographic elements. For instance, the source of halide ions can be jetted into the solution containing the source of silver ions with the alkali salt of the fatty acid. However, the solution of the source of silver ions and the alkali salt of the fatty acid can be added to the source of halide ions. Further, the source of halide ions and the source of silver ions can be added simultaneously to a separate solution containing the alkali salt of the fatty acid. In either case the desired temperature of reaction is maintained in order to provide the desired solution or melt of the reactants.

Maintaining the temperature and pH. of the reactant mixture at the described levels helps provide the desired particle size in the described dispersion.

The time required for reaction can vary depending on the particular source of silver ions, the particular source of halide ions, the alkali salt of the fatty acid, particular concentrations of the reactants and the like. The reaction is normally carried to completion before the temperature and pH of the reaction mixture are lowered.

A suitable pH range for the reactant mixture is about 11.5 to about 12. It is believed that a higher pH can tend to cause undesired fog of the silver halide produced. It is also believed that at lower pH the described alkali salt of the fatty acid becomes undesirably less soluble in the reaction mixture. A higher temperature of the reaction mixture can provide increased solubility of the reactants and accordingly the pH of the reaction could be lower.

After reaction completion, the described temperature and pH of the reaction mixture is lowered, resulting in formation and precipitation of the described solid materials. As described, it is believed that the radiation sensitive silver halide forms first in the reaction and is less soluble at the temperatures and pH range employed such that the silver halide precipitates first followed by the silver salt of the fatty acid. For example, it is believed that silver bromide is less soluble in the described reaction mixture than silver behenate and accordingly, the silver bromide is formed before the silver behenate.

Various mixing means can be employed in the reaction. Extensive mixing has been found not to be necessary. For instance, it has been found that extensive ballmilling can be avoided employed the process described. An ultrasonic probe employed for mixing can be suitable.

In some cases it can be advantageous to add a silver ammonia complex to the reactant mixture. It is believed that the silver ammonia complex provides conversion of any excess fatty acid to the silver salt of the fatty acid. This procedure is described, for example, in U.S. Pat. 3,458,544 of Bryan, issued July 29, 1969. This procedure is employed also in following Example 1.

An especially suitable embodiment of the invention is a method of preparing a dispersion of silver behenate and radiation sensitive silver halide in a liquid medium by (A) admixing, in an aqueous medium, (i) sodium or potassium behenate with (ii) potassium or sodium halide; (B) admixing silver nitrate, in an aqueous medium, with the resulting admixture from (A) to provide a reactant mixture; (C) providing and maintaining the temperature of this reactant mixture at about 75 C. to about 95 C. and the pH of the reactant mixture at about 11.5 to about 12, and mixing the reactant mixture until reaction completion; (D) then lowering the described temperature and pH until the desired dispersion of photosensitive silver bromide and silver behenate is formed.

The resulting product can be recovered as a solid, such as a dry powder and stored for future use.

The dispersion formed according to the described process is useful in photosensitive and thermosensitive compositions or elements for processing with heat. Accordingly, another embodiment of the invention is a method of preparing a photosensitive and thermosensitive composition or element containing such a composition comprising (A) admixing, in an aqueous medium, (i) a water soluble alkali metal salt of a fatty acid with (ii) a source of halide ions; (B) admixing a source of silver ions, in an aqueous medium, with the resulting admixture from (A) to provide a reactant mixture; (C) providing and maintaining the temperature and pH of the reactant mixture at levels at which the water soluble alkali metal salt of the fatty acid is maintained in solution, such as at a temperature of about 75 C. to about 95 C., and mixing the reactant mixture until reaction completion; (D) lowering the temperature to about 20 C. to about 30 C. and lowering the pH of the reactant mixture to about 6; (E) recovering the resulting solid product and mixing it with a reducing agent to provide the desired photosensitive and thermosensitive composition.

For instance, a photosensitive and thermosensitive composition can be prepared by (A) admixing, in an aqueous medium, (i) sodium or potassium behenate, (ii) potassium or sodium bromide; (B) admixing silver nitrate, in an aqueous medium, with the resulting admixture from (A) to provide a reactant mixture; providing and maintaining the temperature of the reactant mixture at about 75 C. to about 95 C. and the pH at about 11.5 to 12; and mixing the reactant mixture until reaction completion; (D) lowering the temperature to about 20 C. to about 30 C. and lowering the pH of the reactant mixture to about 6; then (B) recovering the resulting solid product and mixing it with a reducing agent to provide the desired photosensitive and thermosensitive composition.

It is often desirable to employ, as a source of halide ions, a photographic silver halide emulsion. This is illustrated in the following Example 5. The photographic silver halide emulsion can, for example, be melted and then diluted with water and employed as the source of halide ions in an aqueous medium, as described.

A photosensitive and thermosensitive composition or element, as described can contain (I) an oxidation-reduction image-forming combination containing (a) an oxidizing agent, typically a heavy metal salt, such as silver behenate, with (b) a reducing agent and (II) a catalyst for the image-forming combination, typically radiation sensitive silver halide. The dispersion of radiation sensitive silver halide and heavy metal salt of a fatty acid, prepared, as described, can be employed, respectively, as the catalyst for the image-forming combination and 6 the oxidizing agent part of the image-forming combination.

In addition to the radiation sensitive silver halide in the dispersion prepared according to the invention, the photosensitive and thermosensitive composition or element can contain additional catalyst for the described image-forming combination.

A typical concentration range of catalyst for the described image-forming combination is about 0.005 to about 0.50 mole of catalyst, e.g., radiation sensitive silver halide, per mole of oxidizing agent, such as per mole of silver salt of organic acid, e.g., per mole of silver behenate. A preferred catalyst is silver iodide, silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide, or mixtures thereof.

In cases wherein radiation sensitive silver halide is added to or otherwise used with the photosensitive and thermosensitive composition or element, as described, in addition to the dispersion prepared according to the method of the invention, the additional radiation sensitive silver halide can be coarse or fine-grain, very fine-grain silver halide being especially useful. The radiation sensitive silver halide can be in an emulsion prepared by any of the well-known procedures in the photographic art, such as single-jet emulsions, double-jet emulsions, such as Lippman emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions, such as those described in U.S. Patent 2,222,264 of Nietz et al. issued Nov. 14, 1940; U.S. Patent 3,320,069 of Illingsworth issued May 15, 1967 and U.S. Patent 3,271,157 of McBride issued Sept. 6, 1966. Surface image silver halide emulsions can be used; and, if desired, mixtures of surface and internal image silver halide emulsions can be used, as described, in U.S. Patent 2,996,332 of Luckey et al. issued April 15, 1961. Negative type emulsions can be used. The silver halide emulsion can be a regular grain emulsion such as described in Klein and Moisar, Journal of Photographic Science, volume 12, No. 5, September-October (1964) pages 242-251.

The silver halide emulsions employed in the practice of the invention can be unwashed or washed to remove soluble salts. In the latter case the soluble salts can be removed by chill setting and leaching or the emulsion can be coagulation washed.

The silver halide, which is employed in addition to that prepared according to the invention, can be sensitized with chemical sensitizers, such as with reducing agents; sulfur, selenium, or tellurium compounds; gold, platinum, or palladium compounds, or combinations of these. Suitable procedures are described, for example, in U.S. Patent 1,623,499 of Shepard, issued Apr. 5, 1927; U.S. Patent 2,399,083 of Waller et al., issued Apr. 23, 1946; U.S. Patent 3,297,447 of McVeigh, issued Ian. 10, 1967; and U.S. Patent 3,297,446 of Dunn, issued Ian. 10, 1967.

Radiation sensitive silver halide employed in the practice of the invention can be protected against the production of fog and can be stabilized against loss of sensitivity during keeping.

Suitable organic reducing agents which can be employed in the described image-forming combination include, for example, substituted phenols and naphthols. A bisnaphthol which is especially suitable is a bis-,B-naphthol of the formula:

wherein R and/or R is hydrogen, alkyl with 1 to 3 carbon atoms, alkoxy, e.g., alkoxy containing 1 to 2 carbon atoms, such as methoxy or ethoxy; halogen, nitro, amino or a diazonium group and n is or 1. Suitable bis-fl-naphthols which can be employed include:

2,2-dihydroxy-1,l'-binaphthyl, 6,6-dibromo-2,2-dihydroxy-1,1'-binaphthyl, 6,6-dinitro-2,2-dihydroxy-1,l'-binaphthyl, and/ or Bis- 2-hydroxyl-naphthyl methane.

The described reducing agents are suitable in a range of concentration; however, they are especially suitable, at a concentration from about 0.10 to about 0.75 mole of reducing agent per mole of oxidizing agent, e.g., per mole of silver behenate.

Reducing agents, which are typically silver halide developing agents, can be used in conjunction with or in place of the above bis-naphthol reducing agents. Suitable silver halide developing agents include, for example, polyhydroxybenzenes such as hydroquinone developing agents, e.g., hydroquinone, alkyl-substituted hydroquinones as exemplified by tertiary butylhydroquinone, methylhydroquinone, 2,5 dimethylhydroquinone and 2,6 dimethylhydroquinone; catechols and pyrogallol; halo-substituted hydroquinones such as chlorohydroquinone or dichlorohydroquinone; alkoxy-substituted hydroquinones such as methoxyhydroquinone or ethoxyhydroquinone; methylhydroxynaphthalene; phenylenediamine developing agents; methylgallate; aminophenol developing agents, such as 2,4 diaminophenols and methylaminophenols; ascorbic acid developing agents such as ascorbic acid, ascorbic acid ketols and ascorbic acid derivatives such as those described in US. Patent 3,337,342 of Green, issued Aug. 22, 1967; hydroxylamine developing agents such as N,N'- di(2 ethoxyethyl)hydroxylamine; 3 pyrazolidone developing agents such as 1 phenyl 3 pyrazolidone and 4 methyl 4 hydroxymethyl-1-phenyl-3-pyrazolidone including those described in British Patent 930,572, published July 3, 1963; hydroxytetronic acid, and hydroxytetronimide developing agents, reductone developing agents such as anhydrodihydropiperidino hexose reductone; and the like. Combinations of reducing agents can be employed.

Other, additional, oxidizing agents, which are not silver salts of fatty acids, can be used in combination with the dispersion prepared according to the invention. These include, for example, silver benzoate, silver 4'-n-octadecyloxydiphenyl 4 carboxylate, silver o-aminobenzoate, silver acetamidobenzoate, silver furoate, silver carnphorate, silver p-phenylbenzoate, silver phenylacetate, silver salicylate, silver butyrate, silver terephthalate, silver phthalate, silver acetate and silver acid phthalate.

Oxidizing agents which are not silver salts of a carboxylic acid can be employed, if desired, in combination with the dispersion prepared according to the invention, such as silver phthalazinone, silver benzotriazole and silver saccharin. Oxidizing agents which are not silver salts can be employed, if desired, such as gold stearate, mercuric behenate, auric behenate and the like, but silver salts are preferred.

It is desirable to employed an activator-toning agent in the elements, compositions and processes of the invention to obtain a desired image particularly when phenolic reducing agents are used. A suitable activatortoning agent is a heterocyclic activator-toning agent containing at least one nitrogen atom and of the formula:

where R is hydrogen, hydroxyl, or a metal ion such as potassium, sodium, lithium, silver, gold or mercury; Z, represents atoms completing a heterocyclic nucleus, especially a 5 to 6 member heterocyclic nucleus. The atoms completing the heterocyclic nucleus can be, for example,

or an alkylene group containing 3 to 4 carbon atoms. The atoms completing the heterocyclic nucleus can contain various substituent groups, such as amino, alkyl amino, e.g., methylamino or ethylamino, hydroxyl, carbamyl and the like. An especially suitable activator-toning agent is a heterocyclic activator-toning agent containing at least one nitrogen atom which is preferably a cyclic imide of the formula:

wherein R is hydrogen, hydroxyl, or a metal ion such as potassium, sodium, lithium, silver, gold or mercury; Z represents carbon atoms of a series completing a cyclic imide nucleus, typically consisting of from 5 to 6 carbon atoms, e.g., a phthalimide or succinimide nucleus. The atoms of the cyclic imide nucleus can contain various substituent groups, especially amino, alkyl, such as alkyl containing 1 to 5 carbon atoms, such as methyl, ethyl, propyl, butyl, or pentyl or aryl, such as aryl containing 6 to 20 carbon atoms, such as phenyl, tolyl and xylyl. Suitable activator-toning agents which can be employed in the practice of the invention include:

phthalimide, N-hydroxyphthalimide, N-potassium phthalimide, N-silver phthalimide, N-mercury phthalimide, succinimide, and/or N-hydroxysuccinimide.

The described activator-toning agents are suitable in a range of concentration; however, they are especially suitable at a concentration of about 0.10 mole to about 1.05 moles of activator-toning agent per mole of oxidizing agent, e.g., per mole of silver behenate.

Other so-called activator-toning agents can be employed in combination with or in place of the described cyclic imide activator-toning agents. Typically a heterocyclic organic toning agent containing at least two hetero atoms in the heterocyclic ring of which at least one is a nitrogen atom is employed. These are described, for example, in US. Patent 3,080,254 of Grant, issued Mar. 5, 1963. Suitable toners include, for example, phthalazinone, phthalic anhydride, Z-acetylphthalazinone and 2-phthalylphthalazinone. Other suitable toners are described, for example, in US. Patent 3,446,648 of Workman, issued May 27, 1969.

A non-aqueous, polar, organic solvent such as a compound containing a -O- sor -s02- It I moiety, in a described photosensitive and thermosensitive element or composition suitable for processing with heat can, in many cases, provide improved maximum image densities. Suitable non-aqueous solvents include, for example, tetrahydrothiophene 1,1 dioxide, 4-hydroxybutanoic acid lactone and methylsulfinylrnethane.

A divalent metal salt which has the property of amplifying the developed image can be employed in a described photosensitive and thermosensitive composition or element to cause an increase in maximum image density. A suitable divalent metal salt image amplifier is zinc acetate, cadmium acetate or cupric acetate. The described image-amplifying compounds are suitable in a range of concentration of about 0.005 to about 0.20 mole of divalent metal salt image amplifier per mole of silver salt oxidizing agent; however, they are especially suitable at a concentration from about 0.010 mole to about 0.10 mole of divalent metal salt image amplifier per mole of silver salt oxidizing agent in a composition or element, as described.

It is desirable to employ an image stabilizer precursor in the described photosensitive and thermosensitive elements or compositions. These can be employed in the practice of the invention to reduce the amount of postprocessing print-out due to room light exposure and to reduce the background stain. Suitable stabilizer precursors include azole thioethers and blocked azole thione stabilizer precursors, e.g.,

-acetyl-4-methy1-2- 3-oxobuty1thio) thiazole, 4-furoyl-3-methy1thio-1,2,4-thiadiazole-5-thione,

5 -acetyl-4-methyl-3-( 3-oxobuty1) -thiazoline-2-thione and 2, 6-di-tert-butyl-4-( 1-phenyl-5-tetrazolyl) thiophenol.

The described stabilizer precursors are suitable in a range of concentration; however, they are especially suitable at a concentration from about 0.002 mole to about 0.10 mole of stabilizer precursor per mole of oxidizing agent, e.g., per mole of silver behenate in an element or composition as described.

A range of colorless onium halides can be employed in the described elements or compositions to provide an additional increase in photosensitivity, i.e., speed, and in some cases to obtain a reduction in background density. A suitable speed-increasing onium halide compound is a quaternary ammonium halide, quaternary phosphonium halide and/or a tertiary sulfonium halide, e.g., l-phenethyl-2-picolinium bromide, tetraethylphosphonium bromide or trimethylsulfonium iodide. An optimum concentration can be determined for each onium halide. A suitable onium halide is trimethylphenylammonium bromide which is typically employed at a concentration of about 0.010 mole to about 0.05 mole per mole of catalyst, e.g., per mole of photosensitive silver halide.

A photosensitive and thermosensitive element and com position described and used in the practice of the invention can contain various colloids alone or in combination as vehicles, binding agents and in various layers. Suitable materials are typically hydrophobic but hydrophilic materials can also be employed. They are transparent or translucent and include both naturally-occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as water-solublepolyvinyl compounds like po1y(vinyl pyrrolidone), acrylamide polymers and the like.

Other synthetic polymeric compounds which can be employed include dispersed vinyl compounds such as in latex form and particularly those which increase dimensional stability of photographic materials. Suitable synthetic polymers include those described in U.S. Patent 3,142,586 of 'Nottorf, issued July 28, 1964; U.S. Patent 3,193,386 of White, issued July 6, 1955; U.S. Patent 3,062,674 of Houck et al., issued Nov. 6, 1962; U.S. Patent 3,220,844 of Houck et al., issued Nov. 30, 1965; U.S. Patent 3,287,289 of Ream et al., issued Nov. 22, 1966; and U.S. Patent 3,411,911 of Dykstra, issued Nov. 19, 1968. Effective polymers include water insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, and those which have cross-linking sites which facilitate hardening or curing as well as those having recurring sulfobetaine units as described in Canadian Patent 774,054. Preferred high molecular weight materials and resins include polyvinyl butyral, cellulose acetate butyrate, polymethyl methacrylate, poly(vinyl pyrrolidone), ethyl cellulose, polystyrene, polyvinyl chloride, chlorinated rubber, polyisobutylene, butadiene-styrene copolymers, vinyl chloridevinyl acetate copolymers, copolymers of vinyl acetate, vinyl chloride and maleic acid and polyvinyl alcohol.

The photosensitive and thermosensitive layers and other layers of an element, as described, can be coated on a wide variety of supports. Typical supports include cellulose nitrate film, cellulose ester film, poly(vinylacetal) film, polystyrene film, poly(ethylene terephthalate) film,

polycarbonate film and related films or resinous materials, as well as glass, paper, metal and the like. Typically a flexible support is employed, especially a paper support which can be partially acetylated or coated with baryta and/or an alpha olefin polymer, particularly a polymer of an alpha olefin containing 2 to 10 carbon atoms such as polyethylene, polyproplene, ethylenebutene copolymers and the like.

The photosensitive and thermosensitive and other hardenable layers of an element, as described, can be hardened by various organic or inorganic hardeners, alone or in combination, such as aldehydes, and blocked aldehydes, ketones, carboxylic and carbonic acid derivatives, sulfonate esters, sulfonyl halides and vinyl sulfonyl ethers, active halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, mixed-function hardeners and polymeric hardeners such as oxidized polysaccharides like dialdehyde starch and oxyguargum and the like.

The photosensitive and thermosensitive elements, as described, can contain antistatic or conducting layers.

Such layers can comprise soluble salts such as chlorides,

nitrates and the like, evaporated metal layers, ionic polymers such as those described in U.S. Patent 2,861,056 of Minsk, issued Nov. 18, 1958, and U.S. Patent 3,206,312 of Sterman et al., issued Sept. 14, 1965, or insoluble inorganic salts such as those described in U.S. Patent 3,428,- 451 of Trevoy, issued Feb. 18, 1969. The photosensitive and thermosensitive elements can also contain antihalation materials and antihalation dyes.

The photosensitive and thermosensitive layers or other layers of an element, as described, can contain plasticizers and lubricants. Suitable plasticizers and lubricants include, for example, polyalcohols such as glycerin and diols described, for example, in U.S. Patent 2,960,404 of Milton et al., issued Nov. 1, 1966; fatty acids or esters such as those described in U.S. Patent 2,588,765 of Robijns, issued Mar. 11, 1952; U.S. Patent 3,121,060 of Duane, issued Feb. 11, 1964; and silicone resins such as those described in British 955,061.

The photosensitive and thermosensitive layers or other layers of an element, as described, can contain surfactants such as saponin; anionic compounds such as alkyl aryl sulfonates described, for example, in U.S. Patent 2,600,- 831 of Baldsiefen, issued June 17, 1962; amphoteric compounds such as those described in U.S. Patent 3,133,816, of Ben-Ezra issued May 19, 1964; and adducts of glycidol and an alkyl phenol such as those described in British Patent 1,022,878.

If desired, the photosensitive and thermosensitive elements, as described, can contain matting agents such as starch, titanium dioxide, zinc oxide, silica, polymeric beads including beads described, for example, in U.S. Patent 2,922,101 of Jelley et al., issued July 11, 1961, and U.S. Patent 2,761,245 of Lynn, issued Feb. 1, 1955.

The photosensitive and thermosensitive elements and compositions, as described, can contain brightening agents including stilbenes, triazines, oxazoles, and coumarin brightening agents. Water-soluble brightening agents can be used such as those described in German Patent 972,067 and U.S. Patent 2,933,390 of McFall et al., issued Apr. 19, 1960, or dispersions of brighteners can be used such as those described in German Patent 1,150,274; U.S. Patent 3,406,070 of Oetiker et al., issued Oct. 15, 1968, and French Patent 1,530,244.

The various layers including the photosensitive and thermosensitive layers of an element, as described, can contain light-absorbing materials, filter dyes, antihalation dyes and absorbing dyes such as those described in U.S. Patent 3,253,921 of Sawdey, issued May 31, 1966; U.S. Patent 2,274,782 of Gaspar, issued Mar. 3, 1942; U.S. Patent 2,527,583 of Silberstein et al., issued Oct. 31, 1950; and U.S. Patent 2,956,879 of Van Campen, issued Oct. 18, 1960. If desired, the dyes can be mordanted, for ex- 1 1 ample, as described in U.S. Patent 3,282,699 of Jones et al., issued Nov. 1, 1966.

The photosensitive and thermosensitive layers of an element described can be coated by various coating procedures including dip coating, airknife coating, curtain coating or extrusion coating using hoppers such as described in U.S. Patent 2,681,294 of Beguin, issued June 15, 1954. If desired, two or more layers can be coated simultaneously such as by the procedures described in U.S. Patent 2,761,791 of Russell, issued Sept. 4, 1956, and British Patent 837,095.

As described, the invention is useful in preparing photosensitive and thermosensitive compositions, such as photothermographic compositions. This method is useful, for example, in preparing a photosensitive and thermosensitive composition where an aqueous system is employed. Extensive mixing procedures, such as ball-milling, can be avoided, and conventional silver halide emulsion technology which is desirable can be used. The resulting product provides desired sensitometric properties. Such a method of preparing a photosensitive and thermosensitive composition comprises (A) admixing, in an aqueous medium, (i) a water soluble alkali metal salt of a fatty acid with (ii) a source of halide ions; (B) admixing a source of silver ions in an aqueous medium with the resulting admixture from (A) to provide a reactant mixture; (C) providing and maintaining the temperature and pH of said reactant mixture at levels at which the water soluble alkali metal salt of a fatty acid is maintained in solution and mixing said reactant mixture until reaction completion; (D) lowering said temperature to about 20 C. to about 30 C. and said pH of the reactant mixture to about 6; and (E) recovering the resulting solid product and mixing it with a reducing agent to provide said photosensitive and thermosensitive composition.

A useful preparation of a photosensitive and thermosensitive composition which illustrates this method comprises (A) admixing, in an aqueous medium, (i) sodium or potassium behenate with (ii) potassium or sodium bromide; (B) admixing silver nitrate, in an aqueous medium, with the resulting admixture from (A) to provide a reactant mixture; providing and maintaining the temperature of said reactant mixture at about 75 C. to about 95 C. and said pH at about 11.5 to 12, and mixing said reactant mixture until reaction completion; and (C) lowering said temperature to about 20 C. to about 30 C. and said pH of the reactant mixture to about 6; (D) recovering the resulting solid product and mixing it with a reducing agent to provide the photosensitive and thermosensitive composition, such as after recovering the resulting solid product, mixing it with (i) phthalimide, (ii) 1,1-bi-2-naphthol, (iii) a sensitizing dye, and (iv) a binder, as described in a solvent, also as described, to provide the photosensitive and thermosensitive com osition.

The photosensitive and thermosensitive composition can be coated on a support, as described, to provide a photosensitive and thermosensitive element. An example of preparing a photosensitive and thermosensitive element, according to the invention, comprises (A) admixing, in an aqueous medium, (i) sodium or potassium behenate with (ii) potassium or sodium bromide; (B) admixing (iii) silver nitrate in an aqueous medium with the resulting admixture from (A) to provide a reactant mixture; providing and maintaining the temperature of the reactant mixture at about 75 C. to about 95 C. and the pH of the reactant mixture at about 11.5 to about 12, and mixing the reactant mixture until reaction completion; (C) lowering the temperature to about 20 C. to about 30 C. and the pH of the reactant mixture to about 6; (D) recovering the resulting solid product and mixing it with phthalimide, 1,1-bi-2-naphthol, a sensitizing dye, as described, and a binder, also as described, in a solvent to provide a photosensitive and thermosensitive composition; and (E) coating the photosensitive and thermosensitive composition on a support, such as a paper or film support.

Another embodiment of the invention is a method of preparing a dispersion of radiation sensitive silver halide and a silver salt of a fatty acid, such as silver behenate, in an aqueous medium comprising (A) admixing (i) a molten mixture of a silver halide gelatino emulsion with a sensitizing dye with (ii) an aqueous solution of a watersoluble salt of a fatty acid at about 75 C. to about C., (B) adjusting the pH of the resulting admixture from (A) to about 6 and lowering the temperature to about 60 C., (C) admixing (iii) an aqueous solution of a water-soluble silver salt, such as silver nitrate, with ammonium hydroxide with the admixture from (B), and (D) adjusting the pH of the mixture resulting from (E) to about 6.

Stability to print out from light exposure is increased by employing highly purified materials; for example, freedom from halides and sulfides increase stability to light exposure. The use of highly purified silver behenate can, for example, reduce propensity to print out in background areas of an element prepared according to the invention.

Spectral sensitizing dyes can be used conveniently to confer additional sensitivity to the elements and compositions of the invention. For instance, additional spectral sensitization can be obtained by treating the silver halide with a solution of a sensitizing dye in an organic solvent or the dye can be added in the form of a dispersion as described in British Patent 1,154,781. For optimum results the dye can either be added to the emulsion as a final step or at some earlier stage.

Sensitizing dyes useful in sensitizing silver halide emulsions are described, for example, in U.S. Patent 2,526,632 of Brooker et al., issued Oct. 24, 1950; U.S. Patent 2,503,- 776 of Sprague, issued Apr. 11, 1950; U.S. Patent 2,493,- 748 of Brooker et al., issued Jan. 10, 1950, and U.S. Patent 3,384,486 of Taber et al., issued May 21, 1968. Spectral sensitizers, which can be used, include the cyanines, merocyanines, complex (trinuclear or tetranuclear) cyanines, holopolar cyanines, styryls, hemicyanines such as enamine, hemicyanines, oxonols and hemioxonols. Dyes of the cyanine classes can contain such basic nuclei as the thiazolines, oxazolines, pyrrolines, pyridines, oxazoles, thiazoles, selenazoles, and imidazoles. Such nuclei can contain alkyl, alkylene, hydroxyalkyl, sulfoalkyl, carboxyalky], aminoalkyl, and enamine groups that can be fused to carbocyclic or heterocyclic ring systems either unsubstituted or substituted with halogen, phenyl, alkyl, haloalkyl, cyano, or alkoxy groups. The dyes can be symmetrical or unsymmetrical and can contain alkyl, phenyl, enamine or heterocyclic substituents on the methine or polymethine chain.

The merocyanine dyes can contain the basic nuclei described as well as acid nuclei such as thiohydantoins, rhodanines, oxazolidenediones, thiazolidenediones, barbituric acids, thiazolineones, and malononitrile. These acid nuclei can be substituted with alkyl, alkylene, phenyl, carboxyalkyl, sulfoalkyl, hydroxyalkyl, alkoxyalkyl, alkylamine groups or heterocyclic nuclei. Combinations of these dyes can be used if desired. In addition, supersensitizing addenda which do not absorb visible light may be included such as, for instance, ascorbic acid derivatives, azaindenes, cadmium salts, and organic sulfonic acid as described in U.S. Patent 2,933,390 of McFall et al., issued Apr. 19, 1960, and U.S. Patent 2,937,089 of Jones et al., issued May 17, 1960.

The sensitizing dyes and other addenda used in the practice of the invention can be added from water solutions or suitable organic solvent solutions can be used. The compounds can be added using various procedures including, for example, those described in U.S. Patent 2,912,343 of Collins et al., issued Nov. 10, 1959; U.S. Patent 3,342,- 605 of McCrossen et al., issued Sept. 19, 1967; U.S. Patent 2,996,287 of Audran, issued Aug. 15, 1961; and U.S. Patent 3,425,835 of Johnson et al., issued Feb. 4, 1969.

A range of concentration of spectral sensitizing dye can be employed in the practice of the invention to provide spectral sensitivity. The desired concentration will be influenced by the desired spectral sensitivity, other components in the system, the desired image, processing conditions and the like. Typically a concentration of the described spectral sensitizing dye is about 50 mg. to about 2 grams of spectral sensitizing dye per mole of catalyst, e.g., per mole of photosensitive silver halide.

While concentrations of the various components of the described element or composition can vary depending upon the desired image, the particular components, processing temperature and time and the like, the described element or composition can comprise about 0.10 to about 0.75 mole of the described reducing agent per mole of described oxidizing agent, about 0.005 to about 0.50 mole of the described catalyst per mole of described oxidizing agent, and about 50 mg. to about 2.0 grams of the described sensitizing dye per mole of described catalyst, e.g., per mole of radiation sensitive silver halide.

Processing of a photosensitive and thermosensitive element, as described, is usually carried out under ambient conditions of pressure and humidity. Conditions outside normal atmospheric conditions can be employed, if desired; however, normal atmospheric conditions are preferred.

Various means can be used for providing the desired processing temperature range. The heating means can be, for example, a simple hot plate, iron, roller or the like.

Other addenda known to be useful in photosensitive and thermosensitive compositions and elements of this type, such as described in British Patent 1,161,777, published Aug. 20, 1969; US. Pat. 3,152,904 of Sorensen and Shepard, issued Oct. 13, 1964, and US. Pat. 3,457,075 of Morgan and Shely, issued July 22, 1969, can be employed in the practice of the invention.

Radiation sensitive silver halide as employed herein means silver halide which is sensitive to visible light, and/or X-rays, and/or ultraviolet light, and/or infrared radiation and/or other radiation or matter such as electrons or other particles, which can provide a latent image in or on the silver halide.

Oleophilic, as employed herein, refers to a component which has an afiinity for oils. The degree that the described precipitate comprising a radiation sensitive silver halide and surfactant is oleophilic will depend upon the particular surfactant, the reaction conditions, concentration of components and the like. Example 5 illustrates a typical oleophilic precipitate.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 3.0 grams of behenic acid (also known as docosanoic acid) is dissolved in 1 liter of distilled water at about 80 C. by the drop wise addition of a 50% by weight aqueous sodium hydroxide solution to convert the be henic acid to the soluble sodium salt. 0.203 gram of potassium bromide is dissolved in the hot sodium behenate solution. An aqueous silver nitrate solution containing 0.29 gram of silver nitrate in about 30 milliliters of distilled water is jetted into the hot sodium behenate-potassium bromide solution causing the formation of a silver bromide sol. The pH of the silver bromide sol is slowly adjusted to pH -6 with dilute nitric acid causing the behenic acid to come out of solution as an opaque white dispersion. The temperature of the dispersion is lowered to 60 C. with thorough mixing employing an ultrasonic probe (at maximum output of the commercially available ultrasonic probe sold under the trade name Branson W- 185-D). A solution containing 1.27 grams of silver nitrate in 75 milliliters of water made up to pH 9 with ammonium hydroxide is added to the resulting dispersion. After about 10 minutes, the dispersion is adjusted to about pH 6 and is filtered on a suction filter, washed twice with 14 distilled water and dried under vacuum. This provides a powder containing photosensitive silver bromide, silver behenate and behenic acid.

A photosensitive and thermosensitive element is prepared by dispersing 190 milligrams of the photosensitive silver bromide-silver behenate-behenic acid powder in 4.3 milliliters of a mixture of acetone and toluene (1:1 acetone to toluene by volume) containing 0.031 grams of polyvinyl butyral polymer. The resulting dispersion is mixed with the following components:

0.01% by weight sensitizing dye in acetone-04 ml. 1% by weight phthalimide in acetone-2.0 ml. 3% by weight 1,1-bi-2-naphthol in acetone-13 ml.

After mixing, the resulting composition is coated on a polyethylene coated paper support at a thickness of 6 mils. This provides a photosensitive and thermosensitive element.

The resulting photosensitive and thermosensitive element is exposed sensitometrically light. The element is then processed by contacting it with a hot metal block at 120 C. for 20 seconds. This provides a developed image having a maximum density of 0.90 and a minimum density of 0.34.

When another sample of the photosensitive and thermosensitive element is exposed in the same manner and processed by contacting with a hot metal block at 130 C. for 8 seconds, the resulting developed image has a maximum density of 1.12 and a minimum density of 0.42.

This illustrates the preparation of a photosensitive silver halide-silver behenate dispersion which is in the form of a powder which can be stored until desired for preparation of a photosensitive and/or thermosensitive composition and element. It also illustrates preparation using an aqueous system which avoids the need for extensive mixing procedures such as extensive ball-milling. It is believed that the photosensitive silver halide in the described preparation is formed before the silver behenate due to solubility differences in the system.

EXAMPLE 2 The procedure set out in Example 1 is repeated with certain exceptions. Mixing is carried out using a socalled Dispersator produced by the Premier Mill Corporation using a Simplex Head. Also, the proportions are doubled as a result of this different method of mixing. 6.0 grams of behenic acid is emulsified in 2 liters of distilled Water at C. Fifty percent by weight aqueous sodium hydroxide solution is added dropwise until the resulting composition clears indicating dissolution of the sodium salt of the acid. 0.406 gram of potassium bromide is added to the resulting solution and dissolved. Fifty milliliters of a solution containing 0.583 gram of silver nitrate is jetted into the solution through a stainless steel tube that is projected beneath the surface of the solution. Photosensitive silver bromide is precipitated. After the composition is cooled to room temperature, pH and pAg of the composition is measured. The composition has a pH of 11.85 and a pAg of 7.9. Dilute nitric acid is added slowly to provide a pH of 6 and the mixture is cooled to 60 C. with the mixing device operating at high speed. A solution containing 2.54 grams of silver nitrate in 75 milliliters of water is adjusted to pH 9.0 with ammonium hydroxide and added to the resulting mixture. The pH of the mixture is again lowered to pH 6 using dilute nitric acid. The dispersion is cooled, the resulting solids are filtered using a suction filter, the product is washed with distilled water and dried under vacuum to provide a powder.

A photosensitive composition and element is prepared with the resulting powder using the components and procedure as described in Example 1. The resulting photosensitive and thermosensitive element is sensitometrically exposed to light and processed by contacting the element on a metal block at C. for 20 seconds to provide a 15 developed image having a maximum density similar to those produced in Example 1.

EXAMPLE 3 6.0 grams of behenic acid is dissolved in 2 liters of distilled water at 80 C. with dropwise addition of 50 percent by weight aqueous sodium hydroxide solution as described in Example 1. 0.406 gram of potassium bromide is dissolved in the resulting solution. This solution is cooled to 60 C. About 50 milliliters of a solution containing 3.12 grams of silver nitrate is adjusted to pH 9 using ammonium hydroxide which is jetted into the sodium behenate-potassium bromide solution with the mixing device of Example 2 operating at high speed. The pH of the resulting dispersion is lowered to pH 6 with dilute nitric acid. The resulting solid product is filtered using a suction filter, washed with distilled water and dried under vacuum. This provides a photosensitive powder.

A photosensitive and thermosensitive element is prepared employing the resulting photosensitive powder and the components as described in Example 1. The photosensitive and thermosensitive element is exposed sensitometrically with light and processed by contacting the element on a metal block at 120 C. for 10 seconds. The resulting developed image has a maximum density of 0.70 and a minimum density of 0.34 with similar results at 130 C. for seconds.

While the procedure set out in Examples 1-3 is a socalled batch process, the process of the invention can be modified to provide a continuous process.

It is believed employing the procedures of these examples that the so-called fatty acid soap, i.e., behenic acid soap, is adsorbed to the photosensitive silver halide formed in aqueous suspension changing the surface properties of the solid. It is believed that when the dispersion is subsequently acidified to cause the remainder of the dissolved so-called fatty acid soap to precipitate, that the socalled fatty acid soap-covered photosensitive silver halide particles act as nuclei around which the remainder of the fatty acid precipitates. As a result of this, it is believed that a large number of other compounds can be employed in place of the sodium behenate employed in Examples 1-3. Surfactants which can provide similar results include alkyl pyridinium salts, such as dodecyl pyridinium bromide or octadecyl pyridinium chloride, and alkyl quinolinium salts, such as hexadecyl quinolinium bromide. Quaternary ammonium compounds which can provide similar results also include hexadecyl trimethyl ammonium bromide and dodecyl trimethyl ammonium bromide. Corresponding ternary sulfonium compounds, such as, dodecyl dimethyl sulfonium methyl sulfate or octadecyl methyl benzyl sulfonium methyl sulfate and corresponding phosphonium compounds can provide similar results. The following example illustrates another such material.

EXAMPLE 4 5.0 milliliters each of 0.5 normal silver nitrate and 0.5 normal potassium bromide aqueous solutions are simultaneously run into 1,200 milliliters of distilled water containing 3.3 milliliters of a methanol solution of 1,1-dioctadecyl-2,2'-cyanine-p-toluene sulfonate (2.8 milligrams per milliliters of methanol) with rapid stirring at 80 C. The time for adding the silver nitrate and potassium bromide solutions is 30 seconds. Then 800 milliliters of a solution containing 6.0 gram of behenic acid (behenic acid dissolved by the addition of 50 percent by weight aqueous sodium hydroxide solution to pH 11) at 80 C. is added. Dilute nitric acid is added until the composition has a pH of 6. High speed stirring is maintained with a Dispersator as described in Example 2. A separate solution is prepared by mixing 1.27 grams of silver nitrate in 75 milliliters of water adjusted to a pH of 9 using concentrated ammonium hydroxide. This solution is added to 16 partially convert the behenic acid to the silver salt. Dilute nitric acid is again added to provide a pH of 6. The resulting solid product is filtered using a suction filter, washed with distilled water and dried under vacuum. This provides a photosensitive powder.

A photosensitive and thermosensitive element is prepared employing the procedure and components of Example 1 and the described powder of the present example. The photosensitive and thermosensitive element is sensitometrically exposed with light and processed by contacting the element with a metal block at C. for 15 seconds. The resulting developed image has a maximum density of 0.40 and a minimum density of 0.20.

The following example illustrates that the procedure of the invention can be used employing a conventional photo graphic silver halide gelatino emulsion and a completely aqueous system.

EXAMPLE 5 5.5 grams of a fine-grain silver chloride gelatino emulsion is melted at 40 C. and diluted with about 100 milliliters of distilled water. 3.3 milliliters of a methanol solution of 3,3'-dioctadecyl thiacorbocyanine-p-toluene sulfonate (3 x 10- M solution of dye in methanol) is added to the resulting diluted emulsion. This dye acts as a surfactant and imparts oleophilic properties to the silver halide surface. The so-called dyed emulsion is poured into an aqueous solution of the sodium salt of behenic acid which is at about 80 C. The sodium behenate solution is prepared by dissolving 6.0 grams of behenic acid by dropwise addition of 40% by weight aqueous sodium hydroxide solution in 1 liter of distilled water at 80 C. The pH of the resulting mixture is adjusted to '6 by adding dilute nitric acid and the temperature of the mixture is then lowered to 60 C. A separate solution is prepared by dissolving 1.12 grams of silver nitrate in 25 milliliters of water. Concentrated ammonium hydroxide is then added dropwise to this silver nitrate solution until a clear colorless solution is obtained. The resulting solution is added to the socalled dyed emulsion composition to partially convert the behenic acid to its silver salt. 2.0 grams of photographic gelatin is then dissolved in about 50 milliliters of water and added to the resulting composition. The pH of the composition is then adjusted to 3.85 using dilute nitric acid. The resulting mixture is filtered and recovered as a wet paste.

1.5 grams of the wet paste is dispersed in 3.0 milliliters of an aqueous 5% by weight gelatin solution. The following components are then added to this mixture:

succinimide (0.1 mole in water)2.0 ml.

gelatin (5% by Weight)1.0 ml.

5-(N,N-dihexylaminomethyl-4-phenyl catechol-HCl (0.05

molar solution in methan0l)l.0 ml.

surfactant (2% by weight aqueous solution of Surfactant 10 G distributed by Olin and Matheson Chemical Corporation, U.S.A. and set out in U.S. Patent 3,514,293 of Knox, issued May 26, 1970)-1.0 ml.

water-1.5 ml.

The resulting composition is mixed and coated on a paper support as described in Example 1. The resulting photosensitive and thermosensitive element is exposed sensitometrically to light and then processed by contacting the element with a metal block at a temperature of C. for 30 seconds. The resulting developed image has a maximum density of 0.44 and a minimum density of 0.38. Similar results are obtained when the exposed photosensitive and thermosensitive element is processed by contacting the element with a metal block at C. for 30 seconds.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

What is claimed is:

-1. A method of preparing a dispersion of a radiation sensitive silver halide and a silver salt of a fatty acid in a liquid medium comprising:

(A) providing an oleophilic precipitate comprising radiation sensitive silver halide and a surfactant,

(B) dispersing the oleophilic precipitate in a solution of an alkali metal or ammonium salt of a fatty acid at least at a temperature at which the fatty acid salt is maintained in solution, then,

(C) lowering the temperature and pH of the product of (B) until substantially all of said fatty acid compound is present in said solution as a solid phase, and then (D) converting at least part of said fatty acid compound to a silver salt by admixing a source of silver ions with the product of (C).

2. A method as in claim 1 wherein (A) is carried out by mixing a radiation sensitive silver halide gelatino emulsion with said surfactant.

3. A method as in claim 1 wherein (A) and (B) are carried out by precipitating said radiation sensitive silver halide in a solution of said alkali metal salt of said fatty acid.

4. A method of preparing a dispersion of radiation sensitive halide and a silver salt of a fatty acid in a liquid medium comprising (A) admixing, in an aqueous medium,

(i) a water soluble, alkali salt of a fatty acid with (ii) a source of halide ions; at a temperature of from at least the melting point of said fatty acid to about 95 C.

(B) admixing a source of silver ions, in an aqueous medium, with the mixture from (A) to provide a reactant mixture at said temperature;

(C) providing and maintaining said temperature and pH of said reactant mixture at levels at which the water soluble, alkali salt of the fatty acid is maintained in solution; and mixing said reactant mixture until reaction completion; then (D) lowering said temperature and said pH of the re actant mixture until said dispersion is formed.

5. A method as in claim 4 wherein said fatty acid is behenic acid.

6. A method as in claim 4 wherein said source of silver ions is a water soluble silver salt.

7. A method as in claim 4 wherein said fatty acid is behenic acid, said temperature in (C) is about 75 C. to about 95 C. and said pH in (C) is about 11.5 to about 12.

8. A method as in claim 4 wherein said dispersion of radiation sensitive silver halide and a silver salt of a fatty acid is recovered from said dispersion.

9. A method as in claim 4 wherein said source of silver ions is admixed with said source of halide ions and said alkali metal salt in about stoichiometric proportions.

10. A method of preparing a dispersion of silver behenate and radiation sensitive silver halide in a liquid medium comprising (A) admixing, in an aqueous medium,

(i) sodium or potassium behenate with (ii) potassium or sodium halide (B) admixing silver nitrate, in an aqueous medium, with the resulting admixture from (A) to provide a reactant mixture;

(C) providing and maintaining the temperature of said reactant mixture at about 75 C. to about 95 C. and the pH at about 11.5 to about 12, and mixing said reactant mixture until reaction completion;

(D) then lowering said temperature and pH until said dispersion is formed.

11. A method as in claim 4 wherein said dispersion is (A) mixed with an aqueous solution of a water soluble silver salt with ammonium hydroxide at a pH of about 9 and a temperature of about 20 C. to about 30 C.;

(B) the pH of the resulting mixture is adjusted to about 6 and (C) the resulting product is recovered as a solid.

12. A method of preparing a dispersion of silver behenate and silver bromide in an aqueous medium comprising (A) admixing,

(i) a first aqueous solution, at a temperature of about 75 C. to about C., of sodium behenate with potassium bromide with (ii) a second aqueous solution of silver nitrate with ammonium hydroxide with thorough mixing, said second aqueous solution be at about 60 C. and having a pH of about 9 and (B) reducing the pH of the resulting product until said dispersing is formed.

13. A method of preparing a photothermographic composition comprising:

(A) admixing, in an aqueous medium,

(i) a water soluble alkali metal salt of a fatty acid with (ii) a source of halide irons;

(B) admixing a source of silver ions in an aqueous medium with the resulting admixture from (A) to provide a reactant mixture;

(C) providing and maintaining the temperature and pH of said reactant mixture at levels at which the water soluble alkali metal salt of a fatty acid is maintained in solution and mixing said reactant mixture until reaction completion;

(D) lowering said temperature to about 20 C. to about 30 C. and said pH of the reactant mixture to about 6;

(E) recovering the resulting solid product and mixing it with a reducing agent to provide said photothermographic composition.

14. A method as in claim 13 of preparing a photothermographic composition wherein said fatty acid is behenic acid.

15. A method as in claim 13 of preparing a photothermographic composition wherein said fatty acid is behenic acid, said temperature is about 75 C. to about 95 C. and said pH is about 11.5 to about 12.

16. A method as in claim 13 of preparing a photothermographic composition wherein said source of silver ions is admixed with said source of halide ions and said alkali metal salt in about stoichiometric proportions.

17. A method as in claim 13 of preparing a photothermographic composition comprising (A) admixing, in an aqueous medium,

(i) sodium or potassium behenate with (ii) potassium or sodium bromide;

(B) admixing silver nitrate, in an aqueous medium, with the resulting admixture from (A) to provide a reactant mixture; providing and maintaining the temperature of said reactant mixture at about 75 C. to about 95 C. and said pH at about 11.5 to 12, and mixing said reactant mixture until reaction completion;

(C) lowering said temperature to about 20 C. to about 30 C. and said pH of the reactant mixture to about 6;

(D) recovering the resulting solid product and mixing it with a reducing agent to provide said photothermographic composition.

18. A method as in claim 13 wherein, after said re covering, said resulting solid product is mixed with (i) phthalimide,

(ii) 1,l-bi-2-naphthol,

(iii) a sensitizing dye, and

(iv) a binder in a solvent to provide said photothermographic composition.

19. A method of preparing a photothermographic element comprising (A) admixing, in an aqueous medium,

19 (i) a water soluble alkali metal salt of a fatty acid with (ii) a source of halide ions;

(B) admixing a source of silver ions in an aqueous medium with the resulting admixture from (A) to provide a reactant mixture;

(C) providing and maintaining the temperature and pH of said reactant mixture at levels at which the water soluble alkali metal salt of a fatty acid is maintained in solution and mixing said reactant mixture until reaction completion;

(D) lowering said temperature to about C. to about C. and said pH of the reactant mixture to about 6;

(E) drying the resulting product and mixing it, in a solvent, with a reducing agent and a binder to provide a photothermographic composition; and

(F) coating said photothermographic composition on a support.

20. A method as in claim 19 of preparing a photothermographic element wherein said fatty acid is behenic acid.

21. A method as in claim 19 of preparing a photothermographic element wherein fatty acid is behenic acid, said temperature is about 75 C. to about 95 C. and said pH is about 11.5 to about 12.

22. A method as in claim 19 of preparing a photothermographic element wherein said source of silver ions is admixed with said source of halide ions and said alkali metal salt in about stoichiometric proportions.

23. A method as in claim 19 of preparing a photothermographic element comprising (A) admixing, in an aqueous medium,

(i) sodium or potassium behenate with (ii) potassium or sodium bromide;

(B) admixing silver nitrate in an aqueous medium with the resulting admixture from (A) to provide a reactant mixture; providing and maintaining the temperature of said reactant mixture at about 75 C. to about 95 C. and said pH at about 11.5 to about 12, and mixing said reactant mixture until reaction completion;

(C) lowering said temperature to about 20 C. to about 30 C. and said pH of the reaction mixture to about 6;

(D) recovering the resulting solid product and mixing it, in a solvent, with a reducing agent and a binder to provide a photothermographic composition; and

(E) coating said photothermographic composition on a support.

24. A method as in claim 19 of preparing a photothermographic element comprising (A) admixing, in an aqueous medium,

(i) sodium or potassium behenate with (ii) potassium or sodium bromide;

(B) admixing (iii) silver nitrate in an aqueous medium with the resulting admixture from (A) to provide a reactant mixture; providing and maintaining the temperature of said reactant mixture at about 75 C. to about 95 C. and said pH at about 11.5 to about 12, and mixing said reactant mixture until reaction completion;

(C) lowering said temperature to about 20 C. to about 30 C. and said pH of the reactant mixture to about 6;

(D) recovering the resulting solid product and mixing it with (iv) phthalimide,

(v) 1,1'-bis-2-naphthol,

(vi) a sensitizing dye, and

(vii) a binder, in a solvent to provide a photothermographic composition; and

(E) coating said photothermographic composition on a support.

25. A method of preparing a dispersion of radiation sensitive silver halide and a silver salt of a fatty acid in an aqueous medium comprising (A) admixing (i) a molten mixture of a silver halide gelatino emulsion with a sensitizing dye with (ii) an aqueous solution of a water soluble salt of a fatty acid at about C. to about C.,

(B) adjusting the pH of the resulting admixture from (A) to about 6 and lowering the temperature to about 60 C.,

(C) admixing (iii) an aqueous solution of a water soluble silver salt with ammonium hydroxide with the admixture from (B), and

(D) adjusting the pH of the mixture resulting from (E)to about 6.

26. A method of preparing a dispersion of silver bromide and silver behenate in an aqueous medium comprismg (A) admixing silver nitrate, potassium bromide and a sensitizing dye in an aqueous solvent with thorough mixing at about 75 C. to about 95 C.,

(B) admixing, at about 75 C. to about 95 C., be-

henic acid and sufiicient alkali metal hydroxide with the resulting admixture from (A) to dissolve the behenic acid in the admixture from (A), and

(C) adjusting the pH of the resulting admixture from (B) to about 6 with thorough mixing.

27. The method of claim 26 wherein said silver salt of a fatty acid is recovered in solid form under ambient conditions.

References Cited UNITED STATES PATENTS 3,152,904 10/1964 Sorensen 96--l14.1 3,457,075 7/1969 Morgan 96114.6 3,549,379 12/1970 Hellings 961l4.6 3,617,289 11/1971 Ohkubo 96114.1 3,645,739 2/1972 Ohkubo 96114.1

NORMAN G. T ORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner US. Cl. X.R.

T53 3? UNITED STATES fATEN'f oF F ICE CERTIFICATE OF CORRECTION Patent No. 336L273 Dated Se tember 25, 1973 inventofl Y Warren Miller and Ralph W. Baxendale It isi certified that error appears in the above-identified patent f h and that said Letters Patent are hereby corrected as shown below:

' 'colllmlllla li e 2, "FOR should read ---OF--..

Line 3M; j "the" should read ---wi'th---.

J t Column-2, line 61, after "(A)" (first occurrence), "-J'" shouldffread:I--'-.---. C Column line 58, after lauric" ---,'-1-- should be deleted I t "reading:

" Column A, line 1, that part of the formula reading u 1 H should read 3 3v' I colum 8," line 10, that part of the formula R Q I should read R a I A f r a Column 9, line 47, the entire paragraphbeginnihg with "0 and should not have been set apart from it.

theru is a continuation of the preceding paragraph Column l0 line 7, "polyproplene" should read -polypropylen e---+.

t Column 1 line 20, before "light" should be inserted. V

Page 2 52x 8? III-VIUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,761,273 Dated September 25, 1973 l v warren J. Miller and Ralph w. Baxendale Itis certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 16, line 23, that part of the formula reading "thiacorbqcyanine" should read ---thiacarbocyanine---.

In the Claims I I columneo, 1ine6, that part of the formula reading "bis" should read ---bi---. j

Signed and sealed this 27th day of August-1974.

(SEAL) Attest:

MecoY M. GIBSON ,j' JR. v v c. MARSHALL'DANN Attesting Officer= Commissiq'n er of Patents 

